The present invention relates to cellular telephones, and in particular to a method and system for controlling cellular telephone accessory functions.
Cellular telephones are becoming increasingly xe2x80x9cintelligent,xe2x80x9d with a greater degree of functionality and a more sophisticated user interface. One aspect of this increase in functionality is the ability to control the operation of accessories, such as a vehicle-mounted hands free kit, through the microprocessor in the telephone handset.
Accessories can be classified into two main groups: xe2x80x9cintelligentxe2x80x9d accessories and xe2x80x9cnon-intelligentxe2x80x9d accessories. An xe2x80x9cintelligentxe2x80x9d accessory is one with a microprocessor inside, which is capable of controlling operations of the accessory. A xe2x80x9cnon-intelligentxe2x80x9d accessory lacks a microprocessor and/or the attendant programmability, featuring instead direct hardware-based control of the accessory functions.
Communication between a cellular telephone handset and one or more accessories often occurs by means of a multi-pin connector. The method by which a cellular telephone controls accessory functions has typically depended on the type of accessory. For a non-intelligent accessory, the telephone handset typically controls accessory functions directly using hardware-based controls, which requires that at least one pin of the multi-pin connector be dedicated to the control of each function. Besides being inflexible, this method becomes impractical as the number of controllable accessory functions increases beyond the number of available pins.
For intelligent accessories, communication between the microprocessor in the telephone handset and the microprocessor in the accessory is possible. While this is more flexible than the hard-wired method described above, such CPU-to-CPU communications have typically been executed using a complex language which has a xe2x80x9cvocabularyxe2x80x9d of one or more commands for each function to be controlled. Such a language is unwieldy and memory-intensive.
Thus, a need has arisen for a method and system for controlling cellular telephone accessory functions that addresses the disadvantages and deficiencies of the prior art. Accordingly, a novel method and system for controlling cellular telephone accessory functions is disclosed.
In the method for controlling an accessory function by a cellular telephone, the cellular telephone generates a message payload comprising a command to set a selected register on an accessory device to a selected value. The cellular telephone transmits the message payload to the accessory device. The selected value is stored in the selected register on the accessory device in response to the message payload. The accessory device periodically reads the contents of the selected register. The accessory device controls the accessory function in response to the contents read from the selected register.
In accordance with another aspect of the present invention, a cellular telephone system is disclosed. The system includes an accessory that has a processor with an internal memory. The internal memory has registers controlling respective functions of the accessory. The system also includes a cellular telephone with a processor that generates commands for writing data to the registers of the accessory processor, and transmits the commands to the accessory. The accessory processor receives and follows the commands from the cellular telephone, and reads data from the registers, and updates respective functions of the accessory in response to the data read from the registers. In one embodiment, the accessory processor is capable of writing data to the registers in response to user input received by the accessory.
An advantage of the present invention is that the simple message protocol uses memory and bandwidth resources efficiently. Another advantage of the present invention is that the flexibility of the protocol allows additional accessory functions to be readily controlled without significant modifications to the protocol.